Electricity is traditionally generated by large centralized power plants and transmitted long distances by power distribution systems. To reduce the need for long-distance power generation and dependence upon a few large centralized power plants, electricity is being generated more and more by smaller power generation facilities distributed throughout the macrogrid. Numerous private or municipal entities, for example, are operating modest size photovoltaic and wind power facilities. Such facilities, or a localized grouping of such facilities, are often referred to as microgrids. Although normally connected to the macrogrid, a microgrid can also function autonomously. When operating independent of the macrogrid, the microgrid must control its own frequency and voltage that supply the loads inside the microgrid. Additionally, when the microgrid reconnects to the macrogrid, it must meet certain standards for reconnection. In the USA, these standards are the IEEE 1547.
The Consortium for Electric Reliability Technology Solutions (CERTS) has proposed a microgrid concept in which the microgrid is able to automatically isolate itself in the event of a macrogrid power disturbance or failure without disrupting the power supply to loads within the microgrid. Similarly, the microgrid can automatically reconnects to the macrogrid when it returns to normal. The CERTS microgrid concept thus requires a relatively sophisticated and reliable power system controller. There is thus a need to provide improved and reliable microgrid power system controllers.